Polyolefin compositions

ABSTRACT

Nonhalogen-Containing Thermoplastic Polyolefin blends are provided which are either heat resistant and are particularly useful in wire and cable coatings, extruded profiles, sheet form or injection molded part or have an elastomeric behavior and are particularly useful in injection molded part. These blends comprise preferably (1) ethylene n-butyl acrylate glycidyl methacrylate (EnBAGMA) terpolymer, (2) an ethylene propylene rubber (EPDM) grafted with maleic anhydride, (3) a polypropylene homopolymer for heat resistance or a very low density polyethylene for elastomeric behavior or a linear low density polyethylene (LLDPE) or a low density polyethylene or a high density polyethylene or an ethylene-polypropylene copolymer.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to polyolefin compositions and more particularlyto such compositions which have good heat performance or elastomericcharacteristics, and to shaped articles made from them.

2. Background Discussion

Polyvinyl chloride (PVC) compositions have been on the market for manyyears and are commonly used in a large variety of applications. With thetrend toward a chlorine-free environment, there is in some marketsegments such as construction, automotive and wires and cablesindustries a need for an alternative to PVC. Crosslinked polyolefincompounds or blends of fluoropolymers and PVC have been proposed, thoughboth solution tend to be expensive.

WO 93/19118 and WO 89/06256 disclose PVC-free compositions that aresuitable for use as coatings for electrical cables. These compositionscontain several components that are similar to those described, butlack, i.a, the terpolymer described in the present application.

EP 0 703 271 A1 discloses flexible, halogen-free thermoplasticpolyolefin compositions, including certain which are based upon ethylenevinyl acetate, ethylene vinyl acetate carbon monoxide and very lowdensity polyethylene. While these compositions are useful in manyapplications, they have been found to soften or melt unacceptably undercertain high temperature applications.

SUMMARY OF THE INVENTION

According to the present invention there is provided a polyolefincomposition which has good heat performance or elastomericcharacteristics, is free from halogen-containing and comprises a blendof:

(1) ethylene n-butyl acrylate glycidyl methacrylate terpolymercontaining 30-90% by weight ethylene, 10-70% by weight n-butylacrylateand 0.5-30% by weight glycidyl acrylate or methacrylate,

(2) a polyolefin or rubber selected from the group consisting of (a)ethylene propylene diene methylene rubber (EPDM), (b) a linear lowdensity polyethylene, (c) an ethylene-propylene copolymer, and (d) avery low density polyethylene, or a blend thereof; each of which isgrafted with 0.05-3% by weight of a carboxylic acid or any anhydridethereof, and

(3) a polyolefin selected from the group consisting of (a) polypropylenehomopolymer, (b) very low density polyethylene (c) linear low densitypolyethylene (d) low density polyethylene (e) high density polyethyleneand (f) ethylene-polypropylene copolymer.

Common additives which may be included in the composition of the presentinvention include brominated fillers, aluminium trihydrate or magnesiumhydroxide for flame retardancy, antioxidants, titanium dioxide (for UVresistance and to give a white color to the product), processing aidslike zinc stearate and UV stabilizers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to heat resistant non-halogen containingthermoplastic polyolefin blends which are useful in wire and cablecoatings, extruded profiles, sheet form or injection molded parts, aswell as to elastomeric thermoplastic polyolefin blends which are usefulin injection molded parts. These blends generally are formed bycombining an ethylene n-butyl acrylate glycidyl methacrylate (EnBAGMA)terpolymer, polymer or rubber grafted with maleic anhydride and apolyolefin all of which are chlorine free.

Polymer blends according to the present invention can be formed in wireand cable coatings, extruded profiles, sheet form or injection moldedparts which have many properties comparable to polyvinyl chloride (PVC)containing blends, but with better resistance to heat thanpolypropylene.

Unless otherwise stated, percentage weight ranges for each of thecomponents in the composition of the present invention are calculatedexclusive of any additives which may be present.

The EnBAGMA terpolymer (component (1)) useful in this inventionpreferably contains 30-90% by weight ethylene, 10-70% by weightnbutylacrylate and 0.5-30% by weight glycidyl acrylate or methacrylate,more preferably 50-80% by weight ethylene, 20-35% by weightnbutylacrylate and 0.5-10% by weight glycidyl methacrylate or acrylate.In general, these EnBAGMA's have a melt flow index (MFI) in the range of1-50 g/10 min., preferably in the range of 5-20 g/10 min. as determinedby ASTM D-1238 (measured at 2.16 kg and 190° C.) and are well-known inthe art.

Component (1) preferably comprises 1-40% by weight of the composition ofthe present invention, more preferably 5-25% by weight, still morepreferably 10-20% by weight.

The grafted polyolefin or rubber (component (2)) useful in thisinvention is preferably EPDM grafted with 0.05-3% by weight of maleicanhydride. In general, these EPDM's have a melt flow index (MFI) in therange of 0.05-100 g/10 min., preferably less than 20 g/10 min. asdetermined by ASTM D-1238 (measured at 2.16 kg and 190° C.) and arewell-known in the art.

Component (2) preferably comprises 5-60% by weight of the composition ofthe present invention, more preferably 10-40% by weight, still morepreferably 20-30% by weight.

The polyolefin (component (3)) will be chosen according to whether heatperformance or elastomeric properties are more important for the end useof the composition, as will be known to one skilled in the art. Ingeneral, polypropylene homopolymer (PP) is preferred where heatperformance is most important, and very low density polyethylene (VLDPE)is preferred where elastomeric characteristics are most important.Linear low density polyethylene (LLDPE), high density polyethylene(HDPE), low density polyethylene (LDPE) and ethylene-propylene copolymer(E-PP) will be used for end uses requiring heat performance orelastomeric characteristics that are not extreme.

The terms of VLDPE and LLDPE includes copolymers of ethylene and otheralpha-olefins such as 1-butene, 1-hexene, and 1-octene. The processesfor producing VLDPE, LLDPE, HDPE, LDPE, PP and E-PP are well known inthe art and commercial grades of these polyolefins are available.

Component (3) preferably comprises 20-90% by weight of the compositionof the present invention, more preferably 40-70% by weight, still morepreferably 50-60% by weight.

In addition to its polymer components, the composition of the presentinvention can be blended with maicic anhydride grafted polyolefins ascompatibilizers and/or with common additives such as reinforcing andnon-reinforcing fillers, flame retardant fillers such as brominatedfillers, magnesium hydroxide, aluminium trihydrate, antioxidants, UVstabilizers, lubricants (e.g., oleamide), antiblocking agents,antistatic agents, waxes, coupling agents for fillers, pigments,titanium dioxide, talc and other processing aids (e.g., zinc stearate )known in the polymer compounding art. The pigments and other additivesmay comprise up to about 70 weight percent of the total compositionbased on polymer components plus additives (the polymer components beingpresent in amounts with respect to each other in the proportionspreviously specified); preferably pigments and fillers comprise aboveabout 0 to about 70 weight percent of the total composition.

The blends of the invention can be prepared by mixing the polymericingredients and optional additives by use of conventional masticatingequipment, for example, a rubber mill, Brabender Mixer, Banbury Mixer,Buss-ko kneader, Farrel continuous mixer or twin screw continuous mixer.Mixing times should be sufficient to obtain homogeneous blends andreaction between the glycidyl methacrylate groups of EnBAGMA and themaleic anhydride of the grafted polymer (component 2). Satisfactorymixing times depend upon the type of mixing equipment (shear intensity).Typically, mixing times of about 5 minutes are satisfactory on a batchmixer (Banbury ) while 1.5-2 minutes are satisfactory on a continuousmixer (Brabender, Buss ko-kneader, Farrel or twin screws). If thepolymer blend is obviously non-homogeneous, additional mixing isrequired.

The invention can be further understood by the following examples inwhich parts and percentages are by weight or in parts per hundred rubber(phr) and temperatures are in degrees Celsius.

EXAMPLES 1-4

Legend

MFI=melt flow index

EnBAGMA=ethylene n-butylacrylate glycidyl methacrylate

EPDM=ethylene propylene rubber

MAH=maleic anhydride

VLDPE=very low density polyethylene

LLDPE=linear low density polyethylene

PP=polypropylene homopolymer

Procedure

A blend is prepared by melt-compounding the following components in theproportions set forth in Table 1 below.

EnBAGMA (66.75% ethylene, 28% n-butylacrylate and 5.25% glycidylmethacrylate) having a MFI (190°/2.16 kg) of 12

MAH grafted EPDM (2% MAH) having a MFI (190°/2.16 kg) of 2.0

PP having a MFI (230°/2.16 kg) of 21

MAH grafted PP (0.55% MAH) having a MFI (190°/2.16 kg) of 250

MAH grafted LLDPE (0.85% MAH) having a MFI (190°/2.16 kg) of 40

VLDPE having a density of 0.870 and a MFI (190°/2.16 kg) of 30

Brominated flame retardant filler (SAYTEX 120)

Antimony trioxide flame retardant filler (FSPO 405) available fromChemetron

antioxidant-phenolic type available under the name IRGANOX 1010 fromCiba

Zinc stearate

Melt compounding is carried out on a two roll mill with batches from 100grams at 170-190° C. for ca. 5 minutes. The milled product is formedinto a testing plaque in a hydraulic press at 170-190° C. for 5 minutes.Afterwards stress-strain (tensile strength-tensile elongation) testing(ASTM D-638) Heat Deformation at 90 and 160° C. (a 30 gr weight ishanged to a plate sample having a thickness of 0.5 mm, a length of 10 cmand a width of 10 mm) and permanent set test in tension (ASTM D412) arecarried out. Results are shown in Table 1.

TABLE 1 Example numbers 1 2 Test method EnBAGMA 14 10 MAH grafted EPDM17 25 PP 45.6 — VLDPE — 49.8 MAH grafted PP 9.0 — MAH grafted LLDPE — 15Brominated filler 10 — Antimony trioxide 4 — Antioxidant 0.4 0.2 Tensilestrength 18 MPa 11 MPa ASTM D 638 Tensile elongation 250% 590% ASTM D638 Heat def. at 90° C. 0% 0% (defined in text) Heat def. at 160° C. 0%molten (defined in text) Permanent set in tension — 20% ASTM D 412 ShoreA hardness — 80 ASTM 2240 Specific gravity — 1.05 ASTM 792 Compressionset at 23° C. — 26% ASTM D 395-89 Compression set at 100° C. — 71% ASTMD 395-85 Brittleness temperature — −80° C. ASTM D 1043 Tension set at23° C. — 22% ASTMD 412

One can see that the formulation containing PP shows no deformation at160° C. and therefore has a particularly good resistance to heatdeformation which is a major benefit for automotive primary wires. Onthe other hand, the formulation containing VLDPE shows a relatively highpermanent set value which means good elastomeric behavior which is ofinterest for injection molded parts.

What is claimed is:
 1. A flexible, halogen-free polymer compositioncomprising a blend of (1) ethylene n-butyl acrylate glycidylmethacrylate terpolymer containing 30-90% by weight ethylene, 10-70% byweight n-butylacrylate and 0.5-30% by weight glycidyl acrylate ormethacrylate, (2) a polyolefin or rubber selected from the groupconsisting of (a) ethylene propylene diene methylene rubber (EPDM), (b)a linear low density polyethylene, (c) an ethylene-propylene copolymer,and (d) a very low density polyethylene, or a blend thereof; each ofwhich is grafted with 0.05-3% by weight of a carboxylic acid or anyanhydride thereof, and (3) a polyolefin selected from the groupconsisting of (a) polypropylene homopolymer, (b) very low densitypolyethylene (c) linear low density polyethylene (d) low densitypolyethylene (e) high density polyethylene and (f)ethylene-polypropylene copolymer.
 2. A blend according to claim 1wherein component (1) comprises 1-40% by weight of the blend, component(2) comprises 5-60% by weight of the blend, and component (3) comprises20-90% by weight of the blend.
 3. A blend according to claim 1 whereincomponent (1) comprises 5-25% by weight of the blend, component (2)comprises 10-40% by weight of the blend and component (3) comprises40-70% by weight of the blend.
 4. A shaped article formed from a blendaccording to claim 1.